Play Framework

chore: add commented \`# https.port=9443\` stub to application-skel (PF-90)

Pairs with the existing \`# http.port=9000\` stub. playEnableHttps's
setOrUncomment() helper already detects an existing commented line and
uncomments it in place (rather than appending at end-of-file), so a
fresh app's enable/disable cycle now preserves the line at its original
position in the conf file:

- Fresh scaffold: \`# https.port=9443\` (commented)
- After playEnableHttps: \`https.port=9443\` (uncommented at same line)
- After playDisableHttps: \`# https.port=9443\` (re-commented at same line)
- After playEnableHttps again: \`https.port=9443\` (uncommented; cert reused)

No duplicates accumulate across cycles.

Comment text directs users to the gradle commands explicitly (\`gradle
playEnableHttps\` / \`gradle playDisableHttps\`) so they don't reach
for the python \`play enable-https\` form.